1. Chemsheets AS006 (Electron arrangement)
08/05/2018
Adapted from:
ELECTROCHEMISTRY
Cells and batteries
© A Jul-12

2. Non-rechargeable (primary) cells – Zinc-carbon
-0.80 V Zn(NH3) e- ⇌ Zn NH3
+0.70 V 2 MnO H e- ⇌ Mn2O3 + H2O
Standard cell
Short life
Determine: a) cell emf
b) overall reaction during discharge

3. Non-rechargeable (primary) cells – alkaline
-0.76 V Zn e- ⇌ Zn
+0.84 V MnO2 + H2O + e- ⇌ MnO(OH) + OH-
Determine: a) cell emf
b) overall reaction during discharge
Longer life

4. Non-rechargeable (primary) cells – lithium
Very long life
High voltage
Determine: a) cell emf
b) overall reaction during discharge

5. Rechargeable (secondary) cells
In non-rechargeable (primary) cells, the chemicals are used up so the voltage drops
In rechargeable (secondary) cells the reactions are reversible – they are reversed by applying an external current.
It is important that the products from the forward reaction stick to the electrodes and are not dispersed into the electrolyte.

6. Rechargeable (secondary) cells – Li ion
+0.60 V Li+ + CoO2 + e- ⇌ LiCoO2
-3.00 V Li+ + e- ⇌ Li
Rechargeable
Most common rechargeable cell
Determine: a) cell emf
b) overall reaction during discharge
c) overall reaction during re-charge

7. Rechargeable (secondary) cells – lead-acid
+1.68 V PbO2 + 3 H+ + HSO e- ⇌ PbSO4 + 2 H2O
-0.36 V PbSO4 + H e- ⇌ Pb + HSO4-
Determine: a) cell emf
b) overall reaction during discharge
c) overall reaction during re-charge
Used in sealed car batteries (6 cells giving about 12 V overall)

8. Rechargeable (secondary) cells – nickel-cadmium
+0.52 V NiO(OH) + 2 H2O + 2 e- ⇌ Ni(OH)2 + 2 OH-
-0.88 V Cd(OH) e- ⇌ Cd OH-
Determine: a) cell emf
b) overall reaction during discharge
c) overall reaction during re-charge

9. FUEL CELLS High efficiency (more efficient than burning hydrogen)
How is H2 made?
Input of H2/O2 to replenish so no need to recharge
+0.40 V O2 + 2 H2O + 4 e- ⇌ 4 OH-
-0.83 V 2 H2O e- ⇌ H OH-
Determine: a) cell emf b) overall reaction

11. From wikipedia (public domain)

12. Pros & cons of cells
+ portable source of electricity
Pros & cons of non-rechargeable cells
+ cheap, small
– waste issues
Pros & cons of rechargeable cells
+ less waste, cheaper in long run
– still some waste issues
Pros & cons of fuel cells
+ water is only product
– most H2 is made using fossil fuels, fuels cells expensive